How House Works

MrCool PC 04: inverter compressor drive error

By How House Works EditorialBased on MrCool manualsChecked against sources Updated

MrCool display

PC 04

“Inverter Compressor Drive Error”

DIY 5th Gen, DIY Select, Easy Pro, Advantage 5th Gen, DIY 5th Gen Cassette, DIY Hybrid Air Handler, Olympus Ducted · DIY 5th Gen owner's p. 39; Select service p. 42; Easy Pro service p. 42; Advantage 5th Gen owner's p. 47; DIY 5th Gen cassette owner's p. 45; Hybrid air handler owner's p. 56; Olympus ducted owner's p. 43
Owner checks, then technician

The DIY Select and Easy Pro owner's manuals call PC 04 “Compressor Feedback Protection” (DIY Select Installation & Owner's Manual, p. 41; Easy Pro Installation & Owner's Manual, p. 41); their service manuals use the wording above, and both point to section TS12-S. Service manual: an abnormal compressor drive is found by a detection circuit that checks the communication signal, the voltage and the compressor rotation speed signal (DIY 5th Gen Single-Zone Service Manual, p. 73).

What it means

PC 04 means the outdoor unit’s inverter is not driving the compressor correctly. The DIY 5th Gen service manual says the fault is found by a detection circuit that checks the communication signal, the voltage and the compressor’s rotation speed signal DIY 5th Gen Single-Zone Service Manual, p. 73. More generally, the same manual says the inverter module shuts off on the unit’s current, voltage and temperature; when it does, the indoor unit shows the matching code and the unit stops DIY 5th Gen Single-Zone Service Manual, p. 27.

The name depends on the manual. The DIY 5th Gen, Advantage 5th Gen, cassette, hybrid air handler and Olympus tables say “Inverter Compressor Drive Error”. The DIY Select and Easy Pro owner’s manuals call PC 04 “Compressor Feedback Protection” DIY Select Installation & Owner’s Manual, p. 41; Easy Pro Installation & Owner’s Manual, p. 41. Their service manuals call it “Inverter Compressor Drive Error”, and both documents point to the same section, TS12-S DIY Select Service Manual, p. 42; Easy Pro Service Manual, p. 42. The code and the troubleshooting section are the same; only the name differs.

A unit showing PC 04 may still run. The owner’s manual says that when a code appears the unit may stop operation or continue to run safely DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 38.

Check these first

MrCool’s owner’s manuals give no steps for PC 04 itself. On the DIY 5th Gen, Select, Easy Pro, Advantage 5th Gen, cassette and Olympus manuals the procedure for any error code is:

  1. Wait about 10 minutes; the problem may resolve itself DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 38.
  2. If not, disconnect the power, connect it again and turn the unit on DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 38. The unit cannot be restarted within 3 minutes of being turned off DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 37.
  3. If PC 04 comes back, disconnect the power and contact MrCool with your model number and a description of the problem DIY 5th Gen Single-Zone Installation & Owner’s Manual, pp. 37–38.

The DIY Select, Easy Pro, cassette and Olympus manuals print the same three steps DIY Select Installation & Owner’s Manual, p. 40; Easy Pro Installation & Owner’s Manual, p. 40; DIY 5th Gen Cassette Installation & Owner’s Manual, p. 44; Olympus Ducted Air Handler Installation & Owner’s Manual, p. 41, and so does the Advantage 5th Gen manual, ending with MrCool customer service Advantage 5th Gen Installation & Owner’s Manual, p. 45.

Other series word this step differently. The hybrid air handler manual prints no wait-and-restart step; it says to contact a local dealer or MRCOOL customer service DIY Hybrid Air Handler Installation & Owner’s Manual, p. 54. The 4th Gen E Star and multi-zone manuals print the steps with “roughly 10 minutes” and add “DO NOT attempt these repairs yourself” DIY E Star 4th Gen Installation & Owner’s Manual, p. 41; DIY 4th Gen Multi-Zone Installation & Owner’s Manual, p. 49. The Advantage 4th Gen manual ends the steps with your nearest customer service center Advantage 4th Gen Owner’s and Installation Manual, p. 16. The 4th Gen cassette manual prints no steps; it says to contact a local dealer or the nearest customer service center DIY 4th Gen Cassette Installation & Owner’s Manual, p. 53.

Turn the unit off immediately if you smell burning, hear loud or abnormal sounds, or a fuse blows or the breaker trips frequently; the manual says not to fix these yourself and to contact an authorized service provider DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 37.

When to call a licensed technician

The DIY 5th Gen service manual’s check for PC 04 covers the wiring and connectors between the board and the compressor, how the IPM module is mounted (its screws and silicone grease), the IPM module itself, the outdoor fan and the outdoor unit’s ventilation, and the compressor, before the outdoor board is replaced DIY 5th Gen Single-Zone Service Manual, p. 73. If the outdoor fan is not in working order, the chart refers to the fan speed troubleshooting; the outdoor fan speed code is EC 07. The parts it lists to prepare are connection wires, the outdoor PCB, the IPM module board, the outdoor fan assembly and the compressor DIY 5th Gen Single-Zone Service Manual, p. 73.

This is technician work. The service manual warns that electricity remains in capacitors even when the power supply is off and that they must be fully discharged before troubleshooting DIY 5th Gen Single-Zone Service Manual, p. 35. MrCool’s owner’s manual says electrical work must be completed by a qualified electrical technician and refers repair or maintenance to an authorized service technician DIY 5th Gen Single-Zone Installation & Owner’s Manual, p. 2.

Notes for different models

  • 4th Gen E Star, multi-zone, cassette and Advantage: “Inverter compressor drive error.”, with 5 operation lamp flashes and the timer lamp flashing DIY E Star 4th Gen Installation & Owner’s Manual, p. 41. The DIY 4th Gen multi-zone guide describes PC 04 as the driven chip not detecting the right rotor position of the compressor DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide, Troubleshooting p. 36.
  • Some 4th Gen outdoor main boards have a green and a red LED. For “Inverter compressor drive error” the table gives green off with red flashing, or green flashing with red lit DIY E Star 4th Gen Installation & Owner’s Manual, p. 42. The board is inside the outdoor unit.
  • DIY E Star 3rd Gen: the same wording is code P4 DIY E Star 3rd Gen Installation & Owner’s Manual, p. 39. The Advantage 4th Gen service manual heads its section “P4/PC 04” Advantage 4th Gen Service Manual, Troubleshooting p. 34.

Related MrCool codes

  • P4 “Inverter compressor drive error”
  • PC 00 “ODU IPM Module Protection”
  • EC 07 “ODU Fan Speed Out of Control”

See also

Other ductless mini-splits: Daikin, Fujitsu, Mitsubishi Electric

All MrCool codes

MrCool is a trademark of its owner. How House Works is not affiliated with or endorsed by MrCool.

Sources

  1. MRCOOL. DIY 5th Gen Single-Zone Installation & Owner's Manual. Version Date August 5, 2026; file suffix -01; no document number printed. Cover title: DIY Series Single-Zone Mini-Split System, Installation & Owner's Manual. Accessed Oct 13, 2026.
  2. MRCOOL. DIY 5th Gen Single-Zone Service Manual. Version Date April 20, 2026; file suffix -01; no document number printed; same models as the owner's manual. Accessed Oct 13, 2026.
  3. MRCOOL. DIY Select Installation & Owner's Manual. Version Date August 5, 2026; no file suffix; no document number printed. Accessed Oct 13, 2026.
  4. MRCOOL. DIY Select Service Manual. Version Date April 20, 2026; file suffix -01; no document number printed. Accessed Oct 13, 2026.
  5. MRCOOL. Easy Pro Installation & Owner's Manual. Version Date August 5, 2026; no file suffix; no document number printed. Cover title: MRCOOL DIY Easy Pro Mini-Split System. Accessed Oct 13, 2026.
  6. MRCOOL. Easy Pro Service Manual. Version Date April 20, 2026; no file suffix; no document number printed; covers the DE models. Accessed Oct 13, 2026.
  7. MRCOOL. Advantage 5th Gen Installation & Owner's Manual. Version Date September 19, 2025; file suffix -01; no document number printed. Accessed Oct 13, 2026.
  8. MRCOOL. DIY 5th Gen Cassette Installation & Owner's Manual. Version Date December 02, 2025; file suffix -01; no document number printed. Cover title: DIY Series Outtasight One-Way Cassette. Accessed Oct 13, 2026.
  9. MRCOOL. DIY Hybrid Air Handler Installation & Owner's Manual. Version Date April 21, 2026; file suffix -01; no document number printed. Not linked from MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host.. Accessed Oct 13, 2026.
  10. MRCOOL. Olympus Ducted Air Handler Installation & Owner's Manual. Version Date May 29, 2025; file suffix -01; no document number printed. Cover title: Olympus Series Mid-Static Ducted Air Handler. Accessed Oct 13, 2026.
  11. MRCOOL. DIY E Star 4th Gen Installation & Owner's Manual. Version Date 03-21-23; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host. It prints the same Version Date as the 3rd Gen E Star manual.. Accessed Oct 13, 2026.
  12. MRCOOL. DIY 4th Gen Multi-Zone Installation & Owner's Manual. Version Date 06-06-2023; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host.. Accessed Oct 13, 2026.
  13. MRCOOL. DIY 4th Gen Multi-Zone Troubleshooting & Solutions Guide. Version Date 10-22-21; file suffix -01; pages are numbered within the Troubleshooting section, cited as printed (Troubleshooting 4). A technician document. MrCool's documentation page labels it the owner's manual for 4th Gen DIY.. Accessed Oct 13, 2026.
  14. MRCOOL. DIY 4th Gen Cassette Installation & Owner's Manual. Version Date 06-28-24; file suffix -01; no document number printed. Cover title: DIY Series Outtasight Ceiling Cassette Model DIYCASSETTE**HP-230C25. Accessed Oct 13, 2026.
  15. MRCOOL. Advantage 4th Gen Owner's and Installation Manual. Version Date 09-19-23; file suffix -01; no document number printed. Cover title: Advantage Series Owner's Manual + Installation Manual. It has no code table; the codes for this series come from the service manual.. Accessed Oct 13, 2026.
  16. MRCOOL. Advantage 4th Gen Service Manual. Version Date 7/06/22; file suffix -01; cover title Advantage Series Air Handler & Condenser Service Manual; pages are numbered within sections, cited as printed (Troubleshooting 5). It prints two lamp tables: one with letter codes (E1, P4, P6 and so on) and one with EH, EL, EC and PC codes. This table uses the second.. Accessed Oct 13, 2026.
  17. MRCOOL. DIY E Star 3rd Gen Installation & Owner's Manual. Version Date 03-21-23; file suffix -01; no document number printed. Not listed on MrCool's documentation page on 2026-10-13; the file is on MrCool's own file host. The code table's text layer is scrambled, so it was read from the page image.. Accessed Oct 13, 2026.